At present, there are three types of PC cards whose standards are specified by PCMCIA (Personal Computer Memory Card International Association). All three standard cards have two rows of 34 contact positions each, for a total of 68 contact positions. (Not all card contact positions may include a contact, but each position can hold a contact.) All cards have the same width and length (54 mm.times.85.60 mm) but have different thicknesses in their substrate areas where integrated circuit components may lie. The maximum thicknesses of types I, II, and III are 3.3 mm, 5 mm and 10.5 mm. The type II card is the most popular.
The bus bit architecture of PC cards has been increasing over the last several years from 16 bit to 32 bit architectures, with current proposals to increase to a 64 bit architecture, and with increases in the data rate of signals passing through the contacts. As the data rate increases much above 10 MHz and over 100 MHz, steps have to be taken to provide EMI isolation, as to prevent cross-talk between adjacent signal contacts and to prevent the pick-up and transmission of signals between the card contacts and circuitry in a host. One step has been to add a cardbus shield, which includes a metal plate lying at the top of the front connector and connectable to a secondary ground of the card circuit board. A secondary ground is usually of the same nominal potential as a primary ground, but is isolated therefrom so signals picked up by a large area sheet metal card cover are not coupled to the signal contacts of the front connector. However, at higher data rates, it is found that many separate grounds are required for numerous ones of the contacts. With a 64 bit architecture using 64 bits just for basic signal transmission and the four remaining contacts for power and sensing functions, there are not enough contacts to provide separate grounds for many different signal contacts, even with the cardbus shield in place.
One solution is to provide a new PC card with one or two additional rows of contacts, such as four rows of 34 contact positions each, for a total of 136 contact positions. Of course, a new size host with four rows of contacts would be required to fully receive the new PC card. Because of the large number of existing PC standard cards, especially type II standard cards, a host is still required for such cards. If two separate hosts are to be provided on a compact electronic device such as a personal or laptop computer, then this results in the disadvantage that a lot more volume of the electronic device and a lot more of the surface area of the electronic device is taken up with PC card hosts. A new host for receiving a new card with at least three rows of contact positions, where the new host and new card were constructed so the new host was backward compatible to receive present PC standard cards, especially type II cards, and preferably the other two types as well, would be of value.